This invention relates to an improved overload protecive circuit breaker with bimetal cutoff, adapted for being plugged into a flat-shape fuse female plug socket, which circuit breaker comprises a housing and, in the hollow interior thereof,
a fixed contact element and a bimetal contact element, extending besides each other affixed in a sidewall of the housing, and each being an elongated punched-out part of flat rectangular cross sectional area;
a bimetal snap element fastened on the free end of the bimetal contact element, which snap element extends transversely to the longitudinal axis of the contact elements between their free ends in the interior of the housing;
the bimetal snap element having a contact end and overlapping a fixed contact arranged at the free end of the fixed contact element, and being held with its contact end in contact with bias against the fixed contact.
Such circuit breakers which are push button-actuated are known from the U.S Pat. No. 4,573,031 to Fritz Krasser (corresponding to German Offenlegungsschrift DE 33 42 144 A1 published on May 30, 1985). They are of very small dimensions and can therefore be used as substitutes for flat-shape fusible cutouts. They consist essentially of a housing between the sidewalls of which two contact elements are held in position. One of these two contact eIements is a bimetal contact element and the other one a fixed contact element; they are arranged alongside each other and designed each as an elongated, punched-out part having approximately the shape of a flat right parallelepiped. The external end portions of the two contact elements of the known circuit breaker, i.e those ends thereof which protrude from the housing, have main longitudinal sections extending both in a common plane, while the opposite, inner free ends of the contact elements, i e. those ends thereof which are located in the interior of the housing, have their main longitudinal sections extend in two different, parallel planes, but laterally spaced from each other
(By main longitudinal section of a contact element there is meant the section, extending through that central longitudinal axis of the element, which extends parallel with the broader long faces of the elongated right parallelepiped constituting the element).
Due to this lateral displacement, in addition to the vertical spacing of the two contact elements due to their extending in the two parallel planes, it is made possible for the bimetal snap element, which is arranged between these contact elements, to be located approximately in the main central axial plane of the bimetal contact element and at the same time to overlap the fixed contact element. The snap movement of the snap element can thus take place toward either side from the main extension plane of the bimetal contact element
At the inner free end of the bimetal contact element in the known circuit breaker the bimetal snap element is fastened on one face by a mounting end. The snap element extends transversely to the direction in which the contact elements are moved when being plugged into a female plug socket, and overlaps with its slewable free end opposite its mounting end the inner free end of the fixed contact element. In its rest position, i.e. when it is not heated, the bimetal snap element rests, with a bimetal contact mounted on the slewable free end, with bias on the fixed contact post at the inner end of the fixed contact element
It is a drawback of the known overload protective circuit breakers of this type that the two contact elements extend through the separating joint, between the two shell halves constituting the circuit breaker housing, in approximately the same plane. In doing so, the contact elements rest in special molded recesses of the housing shell halves and are fixed therein, for instance, by means of a pin-and-bore connection. The rigidity of this connection is, however, not very great and does not stabilize sufficiently the positions of the two contact elements relative to one another. In view of the relatively high manufacturing tolerances and the two-part design of the housing, a mutual displacement of the contact elements is relatively easy to happen. Thereby, the cutoff characteristics of an overload protective circuit breaker of this type can be strongly influenced. In practice, this means a high rate of waste in manufacturing, and a relatively broad spread of the cutout time.